Generally, an axial clearance between compressor blades and a compressor housing has a major influence on a compressor efficiency, it holding true that the smaller this clearance is the greater is the compressor efficiency. When, on the other hand, the supercharger, for example the exhaust gas turbocharger, is operated near the pumping limit, a greater clearance can suppress or diminish the compressor pumping during a sudden load change. The axial compressor clearance in this case results from the following component tolerances: compressor housing, bearing housing, axial position of the rotor carrying the compressor wheel and the turbine wheel relative to the axial bearing. In order to be able to achieve as high as possible a compressor efficiency in this case it is therefore desirable to adjust the axial clearance that exists between compressor blades and compressor housing as small as possible. This is possible for example by way of extremely tight tolerances of the individual components, wherein so-called self-grinding-in compressors are obviously also conceivable, in the case of which Teflon is arranged in the axial clearance of the compressor housing where the compressor blades grind themselves in during the operation of the supercharger and because of this have a comparatively small axial clearance.
A further possibility is for example an axial adjustability of the shaft in the bearing housing and an adjustment of the axial clearance that is possible by way of this, as is described for example in the following prior art.
From DE 10 2007 025 130 A1 a generic supercharger with a bearing device for mounting in a shaft hub formed by a housing of the supercharger or connected to the same in a fixed manner located between turbine and compressor wheel via a bearing bush which is floatingly mounted within said hub in a closely delimited manner relative to the hub and the shaft alike is known, in the case of which a secure positioning of the bearing bush is provided by a pin which radially from the hub engages in the bearing bush. The pin itself is rotatable, at least during the assembly, about a pin or centring axis and serves to thereby make possible an adjustment of the axial position of the bearing bush. To this end, the second part of the pin engaging in the bearing bush is formed eccentrically to a first part of the pin rotatably mounted in the bearing housing of the supercharger, wherein in the bearing bush itself for the engagement of the second part of the pin an elongated hole with adjusting play running in the circumferential direction of the bearing bush is provided.
Disadvantageous with the elongated hole described above however is that the same leads to a point contact between the cylindrical pin and the bearing bush as a result of which a comparatively high wear occurs in the region of the point contact which has a negative effect on the play connected with this. In addition there is the risk that the combination of a circle-cylindrical pin and an associated elongated hole leads to a jamming and/or great wear during the adjusting or during the operation.